Would appreciate if anyone can share how to solve the problem of com port in use when trying to upload sketches. I realized that I can only upload new sketches to the board by rebooting with the serial port disabled and enabling it after the system restarted. All this is done with the board plugged in (to force the assignment of port to the board? doesn't seem right either...). It didn't work when I reboot without disabling the serial port.

Anyway to find out which program or device is also using the same com port? Can't find the information in Device Manager.

The strange thing is, regardless of what com port I changed to, the same problem occurred, giving me the impression that Arduino is preventing itself from using the com port (different threads of same program using the com port and blocking the other?).

I tried disabling norton AV, bluetooth, and other programs visible to me without avail.

How about using a different OS ?Windoze for gaming, something useful for the rest.

Can't comment on Vista. It's on my laptop, but only for purpose of reselling it sometime. Never used it, too many colors, ugly explorer.

I know this doesn't help much, but I've long given up thinking about the other OS, expect for running games. XP had become a decent flavour of windoze with SP2, Vista doesn't really exist, the W7 may be better, maybe not.

• Upload doesn't work? Do a loop-back test.• There's absolutely NO excuse for not having an ISP!• Your AVR needs a brain surgery? Use the online FUSE calculator.• My projects: RGB LED matrix, RGB LED ring, various ATtiny gadgets...• Microsoft is not the answer. It is the question, and the answer is NO!

I've posted it in another thread but realized that the problem I encountered is different from the thread starter. Pardon me transferring it here. Hope someone can help.

I realised one thing while trying to figure out the port already in use problem. After getting it to work following the cumbersome way of disabling, rebooting and enabling the serial port, I realised that it may be the ide refusing to release it hold on the port (pardon me if I am technically incorrect with terms and jargons here).

When I quite the IDE and started it again, the uploading works ok. Once I plugged out the USB cable and plug it back again, the problem starts. This occurs regardless of whether I unplug the usb cable with IDE running or after I shutdown the IDE.

So it seems to me that the device still hanging on to the serial port is the IDE than any other program.

Did you solve the problem? I had exactly the same problem on Vista Home Premium. I started to suspect a problem with Vista because I have the same error when trying to synchromize a Palm pilot using bluetooth over a USB connection. Then I loaded the program on an XP machine and worked at the first try.

Nope. Unfortunately. I don't have a XP machine right now. Not enough space to do a dual boot. I'm trying to repair my good old P3 which has some popped caps on its MB and graphic card. If it can be revived, I can do a test.

Portmon also said that the port is in use and cannot connect to it. Replaced the 2 files didn't solve the problem. I got a feeling that the port wasn't "released" by arduino after I removed the USB cable and was still "marked" as being held till I disabled it and do a reboot.

Its very strange your problem, maybe with portmon you can see what thing is capturing your port. First disconnect the arduino, then disable the ftdi driver, then enable it and change the com port number, then connect arduino, checking portmon for misterius port activity